Debates of various kinds are happening all over the world whether asteroids and comets hit the Earth at regular intervals. These debates have been happening for many decades and few studies have shown that large destruction events on Earth happens every 26 million to 30 million years, similar to the one which wiped out the dinosaurs 66 million years ago. Studies also shows that asteroids triggered the extinction of dinosaurs and showers of asteroids could be the reason for regular extinction events. If the studies prove right, then we might able to predict and prevent asteroids from cause mass extinction in the future.
As per studies, there are approximately 190 impact craters from asteroids and comets on Earth which range in size from a few meters to more than 100km across. They are formed between a few years ago to two billion years ago. “Meteor crater” is the one seen in Arizona and only few like this are visible for naked eye. Expert scientists have learned to distinguish impact craters even if they are covered by lakes, ocean or thick sediment layers. Experts suggest that sun has a companion star called Nemesis which come up to the solar system every 26m to 30 m years and causes the showers of comet. Other studies says that sun moves up and down a little bit when it orbits the galaxy, crossing the galactic disk every 30 m years and this could set off comet showers.
But there isn’t any confirmation that asteroids hits earth at regular intervals. But this cannot be believed blindly because craters which are already there disappear as they age even though some are not seen at all because they are found on the ocean floor. The age of a crater is based on radioactive decay or looking at microscopic fossils with known ages. But one cannot be sure about the periodicity and there is no way to forecast when a large asteroid collision may once again threaten life on Earth.